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Identification of strong oral carcinogen in smokeless tobacco by ferujkll sdff
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Identification of strong oral carcinogen in smokeless tobacco |
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The chemical (S)-N'-nitrosonornicotine, or (S)-NNN, which ispresent in smokeless tobacco products, is a strong oral carcinogen,according to results presented at the AACR Annual Meeting 2012,being held March 31 - April 4. Although smokeless tobacco products have long been linked withcertain cancers , including oral cavity cancers and esophageal cancers, this is thefirst study to identify a specific chemical present in smokelesstobacco products that induces oral cancer in animals, according to Silvia Balbo, Ph.D., research associateat the Masonic Cancer Center of the University of Minnesota inMinneapolis, Minn. "(S)-NNN is the only chemical in smokeless tobacco known to causeoral cancer," Balbo said. "This finding provides mechanisticunderpinning for the epidemiologic observations that smokelesstobacco products cause oral cancer." Balbo and colleagues administered two forms of NNN called (S)-NNNand (R)-NNN to four groups of 24 rats. The rats were given either(S)-NNN alone, (R)-NNN alone, a combination of both or tap water.The total dose was approximately equivalent to the amount of(S)-NNN to which a smokeless tobacco user would be exposed fromchronic use of these products.
All rats assigned to (S)-NNN alone or the combination began losingweight after one year of exposure and died by 17 months. Ratsassigned to (R)-NNN or tap water were terminated at 20 months. All rats assigned to (S)-NNN had esophageal tumors and demonstrated100 percent incidence of oral tumors including tumors of thetongue, buccal mucosa, soft palate and pharynx. In contrast,researchers found oral tumors in only five of 24 rats given (R)-NNNand esophageal tumors in three of 24 rats assigned to (R)-NNN.Twelve rats given the combination of (S)-NNN and (R)-NNN had 153esophageal tumors and 96 oral tumors.
"Measures should be taken to reduce this chemical in smokelesstobacco," Balbo said. "If it is not possible to stop the use ofsmokeless tobacco products, we should advocate for a reduction ofthis chemical in these products." Because the Food and Drug Administration regulates tobaccoproducts, Balbo said she hoped these results will inform regulatorydecisions. Moving forward, she and her colleagues hope to identifyother chemicals that may be carcinogens in smokeless tobacco and tounderstand what level of these chemicals is present in smokelesstobacco products. "In addition, we have to understand how this research translates tohuman beings," Balbo added.
"We have to understand the uptake ofNNN from smokeless tobacco products in humans and develop betterbiomarkers, such as urinary biomarkers, to have a tool to monitorthe levels to which smokeless tobacco users are exposed." Balbo believes these findings are yet another affirmation thattobacco products should be avoided. Abstract Smokeless tobacco products, consisting most commonly of moist snuffplaced in the mouth, either directly or in sachets, are gainingpopularity in the U.S. In 2009, 7.0% of men and 11.0% of male highschool students were current users. While smokeless tobacco use isunquestionably less harmful than cigarette smoking, it isnevertheless a recognized cause of oral cancer.
A quantitativelyimportant carcinogen in all smokeless tobacco products isN -nitrosonornicotine (NNN), occurring at levels ranging from 0.4- 17 g/g dry weight in current products consumed in the U.S.These amounts are far higher than those of nitrosamines in otherconsumer products. NNN has a chiral center at its 2 -position andconsequently exists as enantiomers. The major enantiomer in tobaccoproducts is (S)-NNN. Racemic NNN, administered to F-344 rats in thedrinking water, is known to induce tumors of the esophagus in rats,but there are no reports in the literature on the carcinogenicityof (S)-NNN. Based on DNA binding studies of (S)-NNN thatdemonstrated relatively high adduct levels in both the ratesophagus and oral cavity, we initiated a carcinogenicity study.Groups of 24 male F-344 rats, 7 weeks of age, were treated with(S)-NNN or (R)-NNN (15 ppm in the drinking water) or racemic NNN(15 rats, 30 ppm), or were given tap water.
All rats in the groupstreated with (S)-NNN or racemic NNN began losing weight after oneyear of treatment and had died or were euthanized for humanereasons by 17 months of treatment, while the rats given (R)-NNN andthe controls were terminated at 20 months. Tumors were countedblinded to treatment. Necropsy of 20 (S)-NNN treated ratsdemonstrated a 100% incidence of oral tumors and a total of 91 oraltumors, including tumors of the tongue (1.5 tumors per rat), buccalmucosa (1.0), soft palate (0.5), and pharynx (0.75) in addition toesophageal tumors in all rats (6.1 tumors per rat). Some of theoral tumors were 4 mm in size: tongue (9 tumors); buccal mucosa(2); soft palate (4); pharynx (5). (R)-NNN induced oral tumors inonly 5 of 24 rats and esophageal tumors in 3, while racemic NNN wasalso highly active causing 153 esophageal tumors and 96 oral tumorsin 12 necropsied rats.
Preliminary histopathological analysis ofthe tumors indicated that they encompass a spectrum from benignsquamous papillomas to malignant squamous cell carcinomas. Theseresults clearly demonstrate, for the first time, the strongcarcinogenicity of (S)-NNN in the rat oral cavity. Thus, (S)-NNN isthe only potent oral carcinogen identified in smokeless tobacco.There is an urgent need to eliminate this powerful carcinogen fromtobacco products. Additional References Citations. I am an expert from Fashion Accessories Agents, usually analyzes all kind of industries situation, such as cowboy belt buckles , led belt buckle.
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